Medical imaging has been an expanding field for several decades. With increasing diagnostic tools, increasing population, more wide-spread access to medical treatment, and the desirability of sharing information between doctors and professionals, medical imaging is likely to continue growing. To address this continued growth, and the subsequent inconveniences of paper and other fixed forms of medical image storage, the medical community has increasingly turned to digital forms of image storage.
Picture Archiving and Communications Systems (PACS) are a popular example of a digital image system. These systems connect elements such as imaging modalities, storage databases or areas, clients that use the medical image data, and data processing devices to create a network of imaging technology. Such systems then provide easier remote diagnosis and data access, sharing of information between health-care professionals, and ultimately a better health-care system.
In what is termed a “Store and Remember” configuration, a first PACS network can utilize a second PACS network as a long-term storage solution. In this configuration the problem of long-term data storage is offloaded to the second PACS network. This can be useful for many situations and is an instance of buffering or caching as it is known in the industry. This also has the benefit of effectively publishing images to a broader audience that includes users with access to the second PACS network as well as the first. This can be done as either a substitute for other types of long-term storage or in addition to local archival.
In a mirroring configuration, multiple PACS networks can utilize each other as redundant storage locations to ensure that image data files are properly archived (i.e. “mirrored”) to provide additional protection against loss and to allow image data files at one PACS network to be viewed at another PACS network. However, when two or more related PACS networks use each other as redundant storage locations, the resulting flow of image data files being archived can result in what is termed “looping” or cyclic storage activity.
As an illustration of this consider an image data file being sent by a source PACS network to a destination PACS network for archiving (i.e. redundant storage). If the destination PACS network is configured to store to the source PACS network (i.e. to automatically request archiving of any image data file it receives on the source PACS network) then the image data file will unnecessarily be queued up for archiving back to the source PACS network. If the source PACS network is configured to accept duplicates, then the source PACS network will receive the same image data file and again queue the image data file for archiving back to the destination PACS network. However, since the image data file originated from the source PACS network and accordingly is already known and archived at the source PACS network, the image data file does not require re-archiving at the source PACS network.
Such cyclic archiving results in a high and continuous volume of unnecessary image data transmissions between source and destination PACS networks. In addition, if it is not apparent to a destination PACS network whether an image data file has been archived and previously pre-processed and checked at the source PACS network then the destination PACS network may conduct additional unnecessary processing such as OCR, field mappings, HIS verification, and compression.
Most image archiving systems that have been designed for PACS networks either are single-location archives where image data files are not transmitted remotely or utilize a master-slave configuration. In these kinds of image archiving systems, there is only one direction of archiving (i.e. slaves are the only networks that send unsolicited images to their masters) and accordingly, the issue of cyclic archiving is not a concern. However, in situations where there is a master archive that is also a slave to one of it's own slaves (i.e. in PACS archive mirroring), cyclic archiving difficulties are problematic.
The negative impact of “looping” or cyclic archiving on network efficiency can be severely compounded when three or more PACS networks are involved. For example, where an image data file is sent by a first PACS network to a second PACS network for archiving, the second PACS network automatically sends the image data file to a third PACS network for archiving and then the third PACS automatically sends the image data file back to the first PACS network to be re-archived and so on. The negative effects associated with “looping” or cyclic archiving dramatically increase the cost of archiving image data files within a PACS network.